Field Notes Fatigue: Signs and Countermeasures
Fatigued workers perform poorly, behave carelessly, become inattentive, and make more errors. They display decreased motivation, increased irritability, and low morale. Crew leaders should watch for behavior changes and other signs that workers are fatigued.
Fatigue tends to be higher at the midpoint and toward the end of a work shift. Accidents peak during the last 2 hours of a 10-hour day. Alertness begins to decline from 1600 to 2300; after 2300, the likelihood of falling asleep increases dramatically. Sleep-deprived workers may suffer from short, intermittent episodes of fatigue. These episodes are characterized by very brief lapses in the performance of tasks, during which details are missed, accuracy is impaired, and performance is slowed.
Signs of Fatigue- Poor and careless performance
- Greater tolerance for error
- More difficulty concen-trating and thinking clearly
- Inattention to minor but potentially important details
- Increased lapses of attention
- Increased irritability
- Decreased motivation
- Slow reaction time
- Impaired communication and cooperation, particularly when working as a crew
- Complaints of headache, stomach, or other problems
- Feelings of depression
- Poor morale
- Loss of appetite
- Weight loss
While there is no substitute for adequate sleep, rest, or time off, crew leaders can employ some short-term counter-measures to minimize the hazards presented by fatigued workers.
Adapted from Countermeasure. 1998. Army Group Risk Management Pub-lication (19 : 6) and material published in the U.S. Army Crew Endurance Leaders Guide. 1997.
Recommendations to Minimize Fatigue: Fatigue Counter-measures
- Ensure that workers are adequately rested before they begin a work shift.
- Slow the work pace to a moderate level on physically demanding tasks.
- Provide periodic rest breaks to allow physical and mental recovery.
- Alternate between heavy and light tasks.
- Change assignments to prevent boredom.
- Provide breaks, naps, or time off after tasks have been completed.
- Provide nutritional food before, during, and after work.
- Provide energy supplements between meals.
- Provide fluid energy supplementation and make certain it is used.
- Ensure that workers maintain good personal hygiene.
- Maintain high standards of physical fitness and work capacity.
Australian bush firefighters may employ a 24-hour shift on the first day of a 7-day assignment. They work 24 hours (including travel time), followed by 8 hours of rest. They may work up to 16 hours a day for the rest of the 7-day assignment. According to Sue Ellis, health and fitness coordinator for Natural Resources and Environment in Victoria, she is not aware of a reported incident (injury or fatality) that could be attributed to fatigue on the 24-hour work shift.
A 1989 MTDC report notes that the 24-hour work/rest cycle should be considered a management option when the 2:1 work/rest ratio cannot be provided with the two-shift system, or when transportation, logistical, or safety problems exist. The report recommends 12 hours of sleep after the 24-hour shift. Furthermore, the report recommends a 12-hour rest period preceding prolonged work or expected sleep loss. For either shift alternative, the report stated that incident command and dispatching organizations should pay more attention to crew sleep/rest before they are assigned to the first shift on a fire. (Jukkala, A.; Sharkey, B. 1989. A study of wildland firefighting work/rest cycles. Tech. Rep. 8951–2235–MTDC. Missoula, MT: U.S. Department of Agriculture, Forest Service, Missoula Technology and Development Center.)
Fatigue IndexThis fatigue test can be used to evaluate recovery from physical work. The test requires that individuals establish normal values over a period of a few days when they are well rested. These values can be compared to values on mornings following days of hard physical work to evaluate recovery. Studies show that fatigue (as indicated by the fatigue test) is related to decreased performance and immune function. It is easiest to take this test using a heart rate monitor, but manual heart rates can be taken using a radial artery (wrist) or carotid artery (neck) pulse. The test is generally done in the morning, before eating breakfast or drinking stimulants, such as coffee.
Tools Needed
- Heart rate monitor (suggested, but not required)
- Stopwatch for timing
- Metronome (set for 120 beats per minute) or a large clock with sweep hands and clear second markings
- 8-inch (20-centimeter)-high bench
Procedure
After getting up in the morning, before eating breakfast or drinking stimulants, such as coffee:
- Sit quietly in a chair for 3 to 5 minutes until your heart rate is stable.
- Record resting heart rate from the monitor, or take your resting pulse at
the wrist or neck for 10 seconds and multiply the number of heartbeats by six to
get the rate per minute.
- Record resting heart rate from the monitor, or take your resting pulse at
the wrist or neck for 10 seconds and multiply the number of heartbeats by six to
get the rate per minute.
- Start a watch and begin stepping.
- Step up with one foot and then up with the next (so both feet are on bench).
Step one foot down followed by the other so both feet are on the ground. This is done
at the cadence of 120 beats per minute so that each beat represents a step. If an
individual is watching a sweep hand on a clock, the two steps to step up onto the
bench or stair should take 1 second and the two steps to step down should take 1 second.
The entire sequence of stepping both feet onto the bench and both feet back to the
ground should take 2 seconds.
- Step up with one foot and then up with the next (so both feet are on bench).
Step one foot down followed by the other so both feet are on the ground. This is done
at the cadence of 120 beats per minute so that each beat represents a step. If an
individual is watching a sweep hand on a clock, the two steps to step up onto the
bench or stair should take 1 second and the two steps to step down should take 1 second.
The entire sequence of stepping both feet onto the bench and both feet back to the
ground should take 2 seconds.
- After exactly 1 minute of stepping, stop. While standing:
- Note exercise heart rate from the monitor or take the exercise pulse at
your wrist or neck, and sit down immediately.
- Note exercise heart rate from the monitor or take the exercise pulse at
your wrist or neck, and sit down immediately.
- Sit quietly, focusing on relaxation.
- At 30 seconds after stopping exercise, take
your heart rate.
- At 60 seconds after stopping exercise, take your heart rate.
- At 30 seconds after stopping exercise, take
your heart rate.
- Record all heart rates:
- Resting heart rate________
- Exercise heart rate_______
- 30-second recovery heart rate_______
- 60-second recoveryheart rate_______
- Fatigue index sum of heart rates_______
- Resting heart rate________
Understanding the Fatigue Index
The fatigue index is unique for each individual and must be compared to that person’s average index for several days during a rested condition.
The more elevated the daily fatigue index from the rested average, the more likely the individual is not recovering from the prior day’s work and stress, and the more likely the individual will be at risk for depressed immune function and upper respiratory track infections. The following guidelines vary depending on the individual.
Experience with athletes and data from the 2001 fire season would suggest that an individual with an increase in the fatigue index of 30 to 40 beats probably needs a day with reduced work stress. When the morning fatigue index is more than 40 above the resting average, individuals should be assigned duties with low stress until they are recovered to within 30 beats of rested values.
| 0 to 30 above rested | –Not generally a concern |
|---|---|
| 30 to 40 above rested | –Slightly increased risk |
| 40 to 50 above rested | –Increased risk |
| More than 50 above rested | –High risk |
The fatigue test was developed by Steven Gaskill, Ph.D., University of Montana Human Performance Lab-oratory. For more information contact: sgaskill@selway.umt.edu.
